How to [dynamically] pin soft body objects to another mesh?
In order to 'pin' certain vertices of a soft body in place, you can use the Soft Body Goal settings with a Vertex Group.

First select the vertices that you want to pin in Edit mode (Tab). Then add a new Vertex Group and click 'Assign' to assign them to the group. Rename the vertex group to something appropriate such as "Pin".



In the Soft Body Goal settings, set the Strength and Stiffness to high values (the closer to 1.0, the more the vertices will be attached in place to the vertices in the starting mesh that you have 'pinned'.



Only those vertices in the vertex group will be 'pinned' - the rest will continue to behave as Soft Body.

You can then either leave the original mesh in place (so it keeps those pinned vertices static) or Hook the vetices to another mesh so that they are pinned to that other mesh.